Slides for a college course based on "Incident Response & Computer Forensics, Third Edition" by by Jason Luttgens, Matthew Pepe, and Kevin Mandia. Teacher: Sam Bowne Twitter: @sambowne Website: https://samsclass.info/121/121_F16.shtml

1. CNIT 121:
Computer
Forensics
13 Investigating Mac OS X Systems

2. Topics

3. HFS+ and File System
Analysis
• Hierarchical File System features:

4. Nine Structures
1. Boot blocks
2. Volume header
3. Allocation file
4. Extents overflow file
5. Catalog file
6. Attributes file
7. Startup file
8. Alternate volume header
9. Reserved blocks

6. Nine Structures
1. Boot blocks
• First 1024 bytes of volume
• Typically empty on modern systems
2. Volume Header and Alternate Volume Header
•Located 1024 bytes from the beginning of the
volume
•Information about the volume, including the
location of other structures

8. iBored
Disk Editor
for
Mac

9. Mac Timestamps
•All in local time
•HFS+ Volume
•Create date, modify date, backup date,
checked date
•File
•Access, modify, inode change, inode birth
time (file creation)

10. Stat Command
• Shows all four timestamps on Mac

11. Allocation File
• A bit for
every block
• 1 = in use
• 0 = available

12. Extents Overflow File
• "Extents" are
contiguous
allocation
blocks

13. Catalog File
• Details hierarchy of files and folders in the system
• Each file and folder has a unique catalog node ID
(CNID)

14. Attributes File
• Optional
• Used for named forks
• Additional metadata assigned to a file
• Like Microsoft's Alternate Data Streams
• Stores origin of files from the Internet, and tags
like "Green" and "Important"

15. Startup File
• Not used by Mac OS X
• Usually empty

16. File System Services
• Spotlight
• Managed Storage

17. Spotlight
• Metadata indexing and searching service
• Indexers examine the content of files to find
keywords
• Some index entire content, others only import
metadata

18. Spotlight
• Can be used to search a live system
• Not much use for a static acquisition
• Indexes are deleted when a file is deleted
• No tools are available to parse the data stored
by the Spotlight indexer once it's extracted
from a drive image

19. Managed Storage
• New in Mac OS X Lion (10.7)
• Allows apps to continuously save data
• Uses daemon "revisiond"
• Saves data on volumes under the "hidden"
directory
• /.DocumentRevisions-V100

20. Capturing db Files
• Copy them to another folder
• Originals are in use and won't open
• db.sqlite shows files used with timestamps

21. • Consider the file with file_storage_id 6

22. Generations
• 394 versions of that file saved
• With timestamps and other info.

23. Core Operating System Data

24. File System Layout
• Four domains for data classification
• Local
• System
• Network
• User

25. Local Domain
• Applications and configurations that are shared
among all users of a system
• Administrative privileges required to modify
data in this domain
• These directories are in the local domain:

26. System Domain
• Data installed by Apple, and a few specialized
low-level utilities
• Most useful domain for intrusion investigations
because it contains the system logs
• Includes all the traditional Unix structures, all of
which require administrative privileges to
modify
• /bin, /usr, /dev, /etc, and so on, also /System

27. Network Domain
• Applications and data stored here is shared
among a network of systems and users
• In practice, rarely populated with data
• Located under the /Network directory

28. User Domain
• Primary source of data for most other
investigations
• Contains user home directories and a shared
directory
• All user-created content and configurations will
be found under /Users
• High-privilege and Unix-savvy users may break
this model

29. MacPorts Package Manager
• Lets you add BSD packages to your Mac
• Very useful
• Requires command-line developer tools
• Link Ch 13b

30. The Local Domain

31. /Applications
• Nearly every installed application is here
• Application Bundles
• Contain everything an application needs to
run:
• Executable code, graphics, configuration
files, libraries, helper applications and scripts

32. Application Bundles
• Finder treats the bundle as a single file
• Most common extensions

33. Inside the Bundle
• Right-click, Show Package Contents
• Subdirectories
• MacOS, Resources, Library, Frameworks,
PlugIns, SharedSupport
• Developers can put anything in these directories
• VMware Fusion's Library folder contains command-
line utilities to manage the VMware hypervisor

34. Console App

35. Package Contents
• Contains additional metadata
• Time and date stamps show when the app was
installed
• A good place to hide data

36. /Developer
• Used by XCode, Apple's development
environment
• Until recently, all development tools, SDKs,
documentation, and debugging tools were here
• Later versions of XCode moved the tools
• This directory may still be present on some
systems

37. /Library
• /System/Library
• App settings for the operating system
• /Library
• Settings shared between users
• /Users/username/Library
• User-specific settings

38. Application Support
• /Library/Application Support
• /User/username/Library/Application Support
• Settings, caches, license information, and
anything else desired by the developer

39. Caches
• /Library/Caches
• /User/username/Library/Caches
• Temporary data for applications

40. Frameworks
• /Library/Frameworks
• /System/Library/Frameworks
• Drivers or helper applications, for
applications
• Usually nothing significant here

41. Keychains
• /Library/Keychains
• /System/Library/Keychains
• /User/username/Library/Keychains
• Passwords and certificates
• Requires user's password to open

42. Logs
• /Library/Logs
• /User/username/Library/Logs
• Application logs
• Very important to review

43. Preferences
• /Library/Preferences
• /User/username/Library/Preferences
• Application preferences, if the application
allows a system API to manage them
• Stored in .plist files
• Comparable to the Software hive in Windows

44. Receipts
• /Library/Receipts
• /User/username/Library/Receipts
• Files here are updated when an application is
added to the system
• InstallHistory.plist contains information about
every application installed via the OS's
installer or update framework

45. WebServer
• /Library/WebServer
• Apache, installed on every copy of Mac OS X,
is started when a user turns on Web sharing
• This folder is Apache's Document Root

46. File Types
• Used by nearly every application
• Property lists (.plist)
• Tools: plutil on Mac, "plist Explorer" on
Windows
• SQLite databases
• Tools: Firefox Plugin SQLite Manager,
sqlitebrowser

47. The System Domain

48. Traditional Unix Paths
• Some investigations are based entirely on data
found here, such as log files
• /System directory is structured similarly to the
/Library directory
• Locations where applications maintain
persistence
• Requires administrator privileges to create or
modify files

49. Artifacts
• System logs in /var/log
• Databases in /var/db
• Records of printed data in the CUPS log
• System sleep image
• Software imported using MacPorts or Fink, or
compiled in place, may be in /opt

50. The User Domain

51. User-Created Content

52. Specific Sources of
Evidence

53. User and Service
Configuration
• Apple uses LDAP for enterprise management
and Directory Services for local user
management
• Directory Services doesn't use the traditional
Unix files /etc/passwd and /etc/groups
• Data in SQLite databases and binary-formatted
property lists

54. The Evidence
• Directory Service data is in
/private/var/db/dslocal
• Databases (or nodes) for the local system are in
the subdirectory nodes/Default
• My password hash is on the next slide
• More info at links Ch 13c and 13d

55. Password Hash

56. Decoding the Password
Hash

57. Other Configuration Options

58. sqlindex
• In /private/var/db/dslocal
• Maintains creation and modification time for the
plist files in the directory structure
• And information on the relationships between
the data
• Automatically backed up to /private/var/db/
dslocal-backup.xar (a gzip tar file)

59. Analysis of sqlindex
• Shows when a share was created
• Whether an account existed,and its privilege
level

60. User Accounts

61. Sharepoints
• Status of the share for
• AFP (Apple Filing Protocol)
• SMB (Server Message Block)
• FTP (File Transfer Protocol)
• Sharepoint names and share path
• When the share was created

62. Trash and Deleted Files
• Files deleted from USB sticks go into a Trash
folder on the stick, labeled by user ID, like
• /Volumes/USBDRIVE/.Trashes/501

63. System Auditing,
Databases, and Logging
• Open Source Basic Security Module (OpenBSM)
• Powerful auditing system
• Logs:
• File access
• Network connections
• Execution of applications and their command-
line options

64. OpenBSM
• Default configuration doesn't save detailed
information and is of limited use for IR
• Configuration files in /etc/security
• Primary file is audit_control

65. OpenBSM
• This configuration will log everything for all
users, and
• Login/logout, administrative events,
processes, and network activity

66. Helper Services
• Run in background
• Track events or common data
• Maintain state with SQLite databases or
property list
• Examples:

67. Airportd
• Runs in an application sandbox
• Configured in /usr/share/sandbox

68. Airportd Plist

69. Networks

70. System and Application
Logging
• Many log and forensic artifacts in these folders
• Most are in plaintext, some are binary

72. Read with Syslog

73. Other ASL Log Files
• Filenames starting with BB
• Authentication logs from long ago
• Year is 1 year after the correct date

74. Other ASL Log Files
• Filenames starting with AUX
• Backtrace for crashed or abnormally
terminated applications
• Plaintext

75. /private/var/audit
• Read with praudit

76. Example Log Entries
• Erase flash drive
• Failed login attempt

77. Interesting Items in Log
• iCloud connection, Time Machine, iTunes
• Indicates that there are backups of data on
other devices

78. Scheduled Tasks and
Services
• Apple moved from cron to launchd
• Commands to execute at startup

79. Properties for LaunchAgents

80. Application Installers
• When an application is installed, two files are
placed in /private/var/db/receipts
• Bill of Materials (BOM) and plist

81. • BOM contains a complete inventory of files
• Plist contains install date, package identifier,
and path access control lists
Application Installers